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A2SPECTRA: Help

A2SPECTRA - HEAO 1 A2 Spectra


Overview

The A2 experiment was flown on the HEAO-1 satellite, between August, 1977 until January 1979. The experiment consisted of six multi-layer multi-anode collimated gas proportional counters. These were two LEDs (Low Energy Detectors), a MED (Medium Energy Detector), and three HEDs (High Energy Detectors). The first 6-months of mission were dedicated to an all-sky scan after which a pointing phase started. This database accesses the spectra (and associated files) obtained from the A2 MED (small and large field of view) and HEDs (1 and 3 small and large filed of view) detectors during the pointed phase. The spectra were generated for all HEAO-1 A2 pointed observations except for those in more unusual HEAO-1 modes (RAM-11 and "radical RAMs"). Thus the set of spectra created are only a subset (though a fairly complete one) of the entire catalog of HEAO-1 A2 pointed observations.

Data Products

The MED and HEDs have two different field of views a small and a large, which sizes are from various combination of 3.0 X 1.5 degrees 3.0 x 3.0 degrees, 3.0 x 6.0 degrees (FWHM). The collimators were aligned so the 3.0 degree response was aligned with the spin axis. Two sets of spectra are associated to each database entry. In the first set, the source is on the collimator axis. In the second set instead the source is significantly off-axis or not even within the collimator aperture due to the satellite wobbling (here after off-source spectra). A background spectrum for each set was derived using blanck sky observations and associated, using several criteria, to the first set (spectrum with the source on axis) and to the second set (off-source spectrum). Since not always the best background file was choosen additional background files are available from the A2SPECBACK database. For each set the following spectral files are available:
 * 2 MED spectra one for the small and other for the large field of view and
   2 associated background files (all in FITS).
 * 2 HED3 spectra one for the small and other for large field of view and
   2 associated background files (all in FITS).
 * 2 HED1 spectra one for the small and other for the large field of view and
   2 associated background file (all in FITS).
Not all the spectra for each set are present. The first set of files, source on-axis, should be used for a given pointing for spectral analysis (filename suffix _p). The second set instead most likely contains background data or data from near by sources, and/or data from the target at a low collimator angle (filename suffix _po).This set in general is not useful to derive source spectral behaviours, but in a few cases can be used as background spectrum (if not contaminating sources are in the FOV) for the first set of files.

For the MED there is only one response file for all the spectra and this is valid also for the HD1 detector. For the HD3 instead 3 responses are available valid for different days through the mission. The database record for each entry the appropriate response for all the detectors.

A plot viewing the MED-S and HD3-S background subtracted spectra is also available in GIF format.


Note on Count Rates

The area in the file is the nominal on-axis area of the detector and the spectra have not be corrected for the reduction in the collimator efficiency during periods when the source was observed off-axis. Therefore the count rate and the normalization in the spectral fitting maybe be incorrect.

The count rates, the count rate error and exposure in the table were obtained from the MED and HED3 small FOV spectral files. If no files are present the value for these field is set to -99999.


Parameters

Name
The parameter 'name' contains the value stored in the OBJECT keyword of the FITS file.

RA
The RA is the Right Ascension of the detected source.

Dec
The Dec is the Declination of the detected source.

LII
The galactic longitude of the source.

BII
The galactic latitude of the source.

Ms_Count_Rate
Count rate from the spectrum obtained with the MED-S detector. The count rate is background subtracted and calculated in the energy range 2-10 kev, using the nominal exposure (see Note_on_products_countrate).

Ms_Count_Rate_Error
Error on count rate from the MED-S detector.

Ms_Exposure
Exposure given in seconds for the MED-S detector.

H3s_Count_Rate
Count rate from the spectrum obtained with the HD3-S detector. The count rate is background subtracted and calculated in the energy range 8-15 kev), using the nominal exposure (see Note_on_products_countrate).

H3s_Count_Rate_Error
Error on count rate from the HD3-S detector.

H3s_Exposure
Exposure given in seconds for the HD3-S detector.

Start_Date
Date of Observation Start given as DD/MM/YY hh:mm:ss (string).

Stop_Date
Date of Observation Stop given as DD/MM/YY hh:mm:ss (string).

Start_Time
Start time of the observation stored as a short history file key (SHF). SHF is the number of seconds before or after 1 January 1980 at 00:00 hrs UT.

Stop_Time
Stop time of the observation stored as a short history file key (SHF). SHF is the number of seconds before or after 1 January 1980 at 00:00 hrs UT.

GIF_File
Root name for the spectral plot of the MED-S and HD3-S spectra. This product is in GIF format.

Med_Respfile
Root name for the MED response file. The response is valid for the small and large field of view. This product is in FITS format.

Hd1_Respfile
HED-1 response matrix file name

Hd3_Respfile
HED-3 response matrix file name

Meds_Backfile
Root name for the MED-S background file obtained with the small field of view The background file is valid for the spectra obtained for the stable pointing (parameter MEDS_FILE). This product is in FITS format.

Medsobackfile
Root name for the MED-S background file obtained with the small field of view The background file is valid for the spectra obtained for the 'wobble' pointing (parameter MEDSOFILE). This product is in FITS format.

Medl_Backfile
Root name for the MED-L background file obtained with the large field of view The background file is valid for the spectra obtained for the stable pointing (parameter MEDL_FILE). This product is in FITS format.

Medlobackfile
Root name for the MED-S background file obtained with the small field of view The background file is valid for the spectra obtained for the 'wobble' pointing. (parameter MEDLOFILE). This product is in FITS format.

Hd1s_Backfile
Root name for the HD1-S background file obtained with the small field of view The background file is valid for the spectra obtained for the stable pointing (parameter HD1S_FILE). This product is in FITS format.

Hd1sobackfile
Root name for the HD1-S background file obtained with the small field of view The background file is valid for the spectra obtained for the 'wobble' pointing. (parameter HD1SOFILE). This product is in FITS format.

Hd1l_Backfile
Root name for the HD1-L background file obtained with the large field of view The background file is valid for the spectra obtained for the stable pointing (parameter HD1LOFILE). This product is in FITS format.

Hd1lobackfile
Root name for the HD1-L background file obtained with the large field of view The background file is valid for the spectra obtained for the 'wobble' pointing. (parameter HD1LOFILE). This product is in FITS format.

Hd3s_Backfile
Root name for the HD3-S background file obtained with the small field of view The background file is valid for the spectra obtained for the stable pointing (parameter HD3S_FILE). This product is in FITS format.

Hd3sobackfile
Root name for the HD3-S background file obtained with the small field of view The background file is valid for the spectra obtained for the 'wobble' pointing. (parameter HD3SOFILE). This product is in FITS format.

Hd3l_Backfile
Root name for the HD3-L background file obtained with the large field of view The background file is valid for the spectra obtained for the stable pointing (parameter HD3L_FILE). This product is in FITS format.

Hd3lobackfile
Root name for the HD3-S background file obtained with the small field of view The background file is valid for the spectra obtained for the 'wobble' pointing. (parameter HD3LOFILE). This product is in FITS format.

Meds_File
Root name for the MED-S source spectral file obtained with the small field of view. The spectral file is obtained with a stable pointing. (associated background MEDS_BACKFILE). This product is in FITS format.

Medsofile
Root name for the MED-S source spectral file obtained with the small field of view. The spectral file is obtained when the satellite was 'wobbling' around the pointing position (associated background MEDSOBACKFILE). This product is in FITS format.

Medl_File
Root name for the MED-L source spectral file obtained with the large field of view. The spectral file is obtained with a stable pointing. (associated background MEDL_BACKFILE). This product is in FITS format.

Medlofile
Root name for the MED-L source spectral file obtained with the large field of view. The spectral file is obtained when the satellite was 'wobbling' around the pointing position (associated background MEDLOBACKFILE). This product is in FITS format.

Hd1s_File
Root name for the HD1-S source spectral file obtained with the small field of view. The spectral file is obtained with a stable pointing. (associated background HD1S_BACKFILE). This product is in FITS format.

Hd1sofile
Root name for the HD1-L source spectral file obtained with the large field of view. The spectral file is obtained when the satellite was 'wobbling' around the pointing position (associated background HD1LOBACKFILE). This product is in FITS format.

Hd1l_File
Root name for the HD1-L source spectral file obtained with the large field of view. The spectral file is obtained with a stable pointing. (associated background HD1L_BACKFILE). This product is in FITS format.

Hd1lofile
Root name for the HD1-L source spectral file obtained with the large field of view. The spectral file is obtained when the satellite was 'wobbling' around the pointing position (associated background HD1LOBACKFILE). This product is in FITS format.

Hd3s_File
Root name for the HD3-S source spectral file obtained with the small field of view. The spectral file is obtained with a stable pointing. (associated background HD3_BACKFILE). This product is in FITS format.

Hd3sofile
Root name for the HD3-S source spectral file obtained with the small field of view. The spectral file is obtained when the satellite was 'wobbling' around the pointing position (associated background HD3SOBACKFILE). This product is in FITS format.

Hd3l_File
Root name for the HD3-L source spectral file obtained with the large field of view. The spectral file is obtained with a stable pointing. (associated background HD3L_BACKFILE). This product is in FITS format.

Hd3lofile
Root name for the HD3-L source spectral file obtained with the large field of view. The spectral file is obtained when the satellite was 'wobbling' around the pointing position (associated background HD3LOBACKFILE). This product is in FITS format.


Contact Person

Questions regarding the A2SPECTRA database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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